1. Technical Field
The present invention relates to a motor driving apparatus for driving a motor. It further relates to a disk apparatus using the same.
2. Related Art
Recently, as a driving apparatus, of a motor used in office automation equipment or audio and video appliances, an apparatus for driving the motor by changing over current paths electronically through a plurality of transistors has been widely employed.
Generally, such a driving apparatus is used for driving motors in disk apparatuses such as optical disk apparatuses (DVD apparatus, CD apparatus) and magnetic disk apparatuses (HDD apparatus, FDD apparatus).
Disks used in the disk apparatus tend to be higher in density, and a high precision is demanded in rotation of the disk and the rotor for driving and rotating the disk.
Further, from the viewpoint of reduction of size and cost of the apparatus itself, it has been intensively attempted to develop a motor having a decreased number of position detecting elements which are indispensable for composing the motor in the prior art.
FIG. 15 shows a conventional motor, and its operation is briefly described. A rotor 2010 has a field section made of a permanent magnet, and one position detecting element 2041 detects the magnetic field of the field section of the rotor 2010. That is, the output signal of one position detecting element 2041 corresponding to the rotation of the rotor 2010 is input to a position detector 2030, and the position detector 2030 supplies output signals H1, H2, H3 mutually different in ⅓ period into a commutation controller 2060. Further, the commutation controller 2060 outputs two sets of three-phase voltage signals Kp1, Kp2, Kp3, and Kp4, Kp5, Kp6 corresponding to the entered signals H1, H2, H3. Upside power transistors 2021, 2022, 2023 are controlled in its current conduction by voltage signals Kp1, Kp2, Kp3, and downside power transistors 2025, 2026, 2027 are controlled by voltage signals Kp4, Kp5, Kp6. As a result, driving voltages of three phases are supplied to the coils 2011, 2012, 2013.
Further, in a conventional motor, in order to perform stable control in a wide range of rotational speed, it is configured to control commutation by one position detecting element in low rotational speed at which a large change in rotational speed may occur, whereas in high rotational speed only in which a small change in rotational speed may occur, without using an output signal of the position detecting element, to control commutation by detecting a counterelectromotive force generated in the coil (see, for example, patent document 1).
In another conventional motor, the rotor position is detected by one position detecting element, and thus position on control may be detected erroneously in a sudden action of the rotor. Therefore, in order to avoid such inconvenience, continuous periods of the output signal of one position detecting element is measured, and increase or decrease of the rotor rotating speed is detected, and stopping control is performed after detection of the reverse rotation of the rotor (see, for example, patent document 2).    Patent document 1: JP 2000-350485A    Patent document 2: JP 06-223489A
The prior art documents, however, relate to a motor in which the current is supplied to the coil on the basis of the estimated electric angle by the output of one position detecting element. The commutation control means depending on the output of one position detecting element involves the following problems.
In the patent document 1, since only the output of one position detecting element can be obtained as the rotation information, the rotating speed can be detected; but the rotating direction cannot be detected. Hence, in the case of stopping action by generating a reverse torque, the rotor can be once stopped by reverse torque, but the reverse torque may be further generated to provide rotation in reverse.
As a means for solving this problem, for example, in patent document 2, for the stopping operation, a pulse interval of two or more speed detection pulses depending on the rotation is measured and compared, and then increase or decrease of rotating speed is detected to detect an inverting phenomenon of rotation. When inverting phenomenon takes place, supply of current to the coil is stopped, and thereby the inverting phenomenon is prevented and stopping action is enabled. In patent document 2, however, since the brake control is started after actually detecting the inverting phenomenon, occurrence of inverting phenomenon cannot be prevented in advance. Besides, the brake control is performed by stopping current supply to the coil, and thus after the start of the brake control, motor rotation is in free-run state, and it takes a very long time until the motor is stopped completely. Further, since the increase or decrease of rotating speed is detected all the time, if a wrong speed detection pulse is measured and compared, supply of current to the coil may be stopped at a rotating speed actually not leading to reverse rotation.
In the disk apparatus for reproducing a DVD-ROM, CD-ROM, CD or the like, the rotating operation is demanded in a wide range of speed, from fast reproduction of 10,000 rpm to 200 rpm for CD reproduction, and it is demanded that the rotation driving should be stable in this rotating speed range. In a programmable disk apparatus such as DVD-RAM/RW device, because information is recorded and reproduced in a high density disk, the disk must be rotated at high precision in recording and reproducing of the disk. Not only in the optical disk apparatus, but also in the HDD, FDD and other magnetic disk apparatus, it is desired that the apparatus be manufactured at low cost, and realize stable disk rotation and driving.